/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.servlet.jsp.tagext;

/**
 * The auxiliary interface of a Tag, IterationTag or BodyTag tag handler that
 * wants additional hooks for managing resources.
 * 
 * <p>
 * This interface provides two new methods: doCatch(Throwable) and doFinally().
 * The prototypical invocation is as follows:
 * 
 * <pre>
 * h = get a Tag();  // get a tag handler, perhaps from pool
 * 
 * h.setPageContext(pc);  // initialize as desired
 * h.setParent(null);
 * h.setFoo(&quot;foo&quot;);
 * 
 * // tag invocation protocol; see Tag.java
 * try {
 *   doStartTag()...
 *   ....
 *   doEndTag()...
 * } catch (Throwable t) {
 *   // react to exceptional condition
 *   h.doCatch(t);
 * } finally {
 *   // restore data invariants and release per-invocation resources
 *   h.doFinally();
 * }
 * 
 * ... other invocations perhaps with some new setters
 * ...
 * h.release();  // release long-term resources
 * </pre>
 */

public interface TryCatchFinally {

	/**
	 * Invoked if a Throwable occurs while evaluating the BODY inside a tag or
	 * in any of the following methods: Tag.doStartTag(), Tag.doEndTag(),
	 * IterationTag.doAfterBody() and BodyTag.doInitBody().
	 * 
	 * <p>
	 * This method is not invoked if the Throwable occurs during one of the
	 * setter methods.
	 * 
	 * <p>
	 * This method may throw an exception (the same or a new one) that will be
	 * propagated further up the nest chain. If an exception is thrown,
	 * doFinally() will be invoked.
	 * 
	 * <p>
	 * This method is intended to be used to respond to an exceptional
	 * condition.
	 * 
	 * @param t
	 *            The throwable exception navigating through this tag.
	 * @throws Throwable
	 *             if the exception is to be rethrown further up the nest chain.
	 */

	void doCatch(Throwable t) throws Throwable;

	/**
	 * Invoked in all cases after doEndTag() for any class implementing Tag,
	 * IterationTag or BodyTag. This method is invoked even if an exception has
	 * occurred in the BODY of the tag, or in any of the following methods:
	 * Tag.doStartTag(), Tag.doEndTag(), IterationTag.doAfterBody() and
	 * BodyTag.doInitBody().
	 * 
	 * <p>
	 * This method is not invoked if the Throwable occurs during one of the
	 * setter methods.
	 * 
	 * <p>
	 * This method should not throw an Exception.
	 * 
	 * <p>
	 * This method is intended to maintain per-invocation data integrity and
	 * resource management actions.
	 */

	void doFinally();
}
